Registration requirement: taxable persons must apply for GST registration in each State where liable, subject to verification. Every person liable under Schedule III must apply for registration in each State where liable, following prescribed procedures; persons registered earlier follow transition rules. Separate registrations may be obtained for distinct business verticals and non-liable persons may register voluntarily. Registration generally requires a Permanent Account Number, though non-residents may use other prescribed documents. Specialized international bodies and notified classes obtain a Unique Identity Number for specified purposes. The proper officer may proceed to register defaulters; applications and UID requests are subject to prescribed verification, notice and opportunity to be heard before rejection, and are deemed granted if no deficiency is communicated within the prescribed period.